Soluble Silver Acetylide for the Construction and Structural Conversion of All-Alkynyl-Stabilized High-Nuclearity Homoleptic Silver Clusters

Silver
acetylide complex [Ag­(ArCC)]n (Ar
= 3,5-di-tert-butylphenyl) with unprecedented
high solubility in common organic solvents has been designed and synthesized.
The high solubility is due to two bulky tert-butyl
substituents on the phenyl ring. This feature is significant to construct
and isolate single crystals of all-alkynyl-stabilized silver clusters,
which are crucial to investigate the intrinsic binding interaction
and coordination modes between Ag­(I) and ethynide ligands. Crystallization
of [Ag­(ArCC)]n under various conditions
resulted in three high-nuclearity homoleptic silver acetylide clusters,
namely, [Ag21(ArCC)20]­(OH) (1), [Ag16(ArCC)16] (2),
and [Ag15(ArCC)15] (3).
Complex 1 has a [Ag21] cluster protected by
twenty 3,5-di-tert-butyl-phenylethynide ligands.
Complexes 2 and 3 have neutral [Ag16] and [Ag15] clusters, respectively. In addition to these
homoleptic silver clusters, two new silver acetylides [Ag20(ArCC)16(CH3COO)4] (4) and [Ag22(ArCC)16(NO3)4(CH3CH2OH)4]­(OH)2 (5) were synthesized. The acetate and nitrate
anions in these structures are more like counterions instead of acting
as critical building blocks or templates for cluster assembly. These
results illustrated the significance of 3,5-di-tert-butyl-phenylethynide ligands in the construction and stabilization
of high-nuclearity silver clusters. Analysis of structures of 1–5 revealed several novel coordination
modes between Ag­(I) and ethynide ligands, which contributed considerably
to our knowledge of Ag­(I)–ethynide binding interactions.